Option 1 states that the velocity increases as the ray passes from a rarer to a denser medium. This is incorrect. When a ray of light passes from a rarer medium (like air) to a denser medium (like glass or water), it slows down and its velocity decreases. Therefore, option 1 is not correct.
Option 2 states that the velocity decreases as the ray passes from a denser to a rarer medium. This is also incorrect. In this scenario, when the ray of light passes from a denser medium to a rarer medium, it speeds up and its velocity increases. Therefore, option 2 is not correct.
Option 3 states that the velocity decreases as the ray passes from a rarer to a denser medium. This is the correct statement. As mentioned earlier, when light enters a denser medium, it slows down and its velocity decreases. Therefore, option 3 is the correct answer.
Option 4 states that the change of velocity does not depend on the nature of the medium. This is incorrect. The change in velocity of light is directly related to the change in the refractive index of the medium it is passing through. Therefore, option 4 is not correct.
In conclusion, option 3 is